As the Internet develops rapidly, the technology of the Internet of Things (IoT) attracts significant attention increasingly and is applied extensively to various fields of daily lives.
The IoT enables interconnection of physical entities with connecting capability in the Internet. In the IoT, each physical entity may be accessed or controlled via the network. By means of the IoT, centralized management and manipulation may be performed on equipment, machines, and objects. The applications of the IoT is extremely extensive, including smart living environments, health and medical applications, and guard against burglary for belongings.
An optical communication system is a communication system using light waves as the transmission media. Although light waves and wireless radio waves are both a kind of electromagnetic waves, the frequency of the former is higher than that of the latter. Besides, the wavelength of light waves is shorter than that of wireless radio waves. These properties enable an optical communication system to have the advantages of high security, no electromagnetic interference (EMI), and high information capacity.
Normal optical communication systems adopt optic fibers, laser, infrared light, or ultraviolet light. According to the wavelength, optical communication systems may be classified into invisible-light and visible-light optical communication systems. Both types of optical communication systems may be used for data transmission.
In addition, thanks to the advantage of no EMI, optical communication systems may be applied in special places such as hospitals and airplanes. Thereby, optical communication is suitable for the communication in the IoT.
The receivers in an optical communication system may be categorized into active and passive receivers. Due to the requirement of an external power supply for providing extra driving power for an active receiver, the volume of the equipment having active receivers in increased. The demand of frequent replacement of batteries also makes the time of continuous usage inadequate. Beside, because the power cord should be connected to the power supply, the location for installing the equipment is limited. These are unfavorable to IoT applications. On the other hand, passive receivers have slower frequency response, resulting limited bandwidth of the received signals.
Currently, a solar panel is developed as the receiver of an optical communication system. The solar panel receives the lighting light, and the information contained in the lighting light may be extracted from the waveform of the output signal
Nonetheless, when a solar panel acts as the receiver in an optical communication system, it is a passive receiver. As shown in FIG. 1, which shows an eye diagram of the transmission rate when using a solar panel as the receiver of an optical communication system, it is known that the transmission rate is only around 0.01 Mbit/s. Accordingly, an optical communication system is required to improve the transmission rate of using a solar panel as the receiver.